Solid-state amplifier circuits typically include transistors that are mounted to printed wiring boards (PWBs). The PWBs are mounted to pallets, which are typically heat sinks that draw heat from the componentry. In a typical configuration, the printed wiring board includes an opening into which the transistor is inserted. The transistor leads are connected to the PWB and the bottom of the transistor casing may be soldered to the heat sink.
Soldering the casings (electrical ground) of the transistors to the metallic heat sinks provides a number or performance advantages. In the case of high-powered RF transistors, soldering transistor casings to heat sinks can result in significant improvements in both thermal and RF performance. The nature of the solder joint between the two surfaces is critical to transistor performance. Optimal solder joints must cover a significant portion of the surfaces and must be of controlled thickness.
In one known method of attachment, solder preforms are used to join transistor casings to heat sinks. Solder preforms provide the type of joint control required to optimize transistor performance. However, in order to ensure proper adhesion between the joined surfaces when using a solder preform, the transistor must be pressed against the heat sink with a predetermined and evenly distributed force while the joint is being soldered.
Accordingly, there is a need for an apparatus that can be used to position and secure a transistor to a heat sink with a prescribed force, to permit the transistor to be soldered to the heat sink in an effective, quick, accurate, and repeatable manner.